1. Field of the Invention
This invention relates generally to magnetic heads and methods of making the same, and more particularly to magnetic write heads having vertically laminated back gap structures and methods of making such heads.
2. Description of the Related Art
A write head is typically combined with a magnetoresistive (MR) or giant magnetoresistive (GMR) read head to form a merged head. In one conventional design, the write head is made of first and second pole pieces having first and second pole tips, respectively, which terminate at an air bearing surface (ABS). The first and second pole pieces are connected at the back gap, whereas the first and second pole tips are separated by a non-magnetic gap layer. An insulation stack, which comprises a plurality of insulation layers, is sandwiched between the first and second pole pieces and a coil layer is embedded in this insulation stack. A processing circuit is connected to the coil layer for conducting write current through the coil layer which, in turn, induces write fields in the first and second pole pieces. Thus, write fields of the first and second pole tips at the ABS fringe across the gap layer. In a magnetic disk drive, a magnetic disk is rotated adjacent to, and a short distance (fly height) from, the ABS so that the write fields magnetize the disk along circular tracks. The written circular tracks then contain information in the form of magnetized segments with fields detectable by the read head.
One or more merged heads may be employed in a magnetic disk drive for reading and writing information on circular tracks of a rotating disk. A merged head is mounted on a slider that is carried on a suspension. The suspension is mounted to an actuator which rotates the magnetic head to locations corresponding to desired tracks. As the disk rotates, an air layer (an “air bearing”) is generated between the rotating disk and an air bearing surface (ABS) of the slider. A force of the air bearing against the air bearing surface is opposed by an opposite loading force of the suspension, causing the magnetic head to be suspended a slight distance (flying height) from the surface of the disk.
Improved techniques for making magnetic heads have become increasingly important for proper head performance and fabrication. Magnetic head assemblies are typically made of multiple thin film layers which are patterned to form various shaped layers in the head. Some of the layers are electroplated, while other layers are sputter deposited over a wafer substrate.
The conventional method of forming a yoke of a magnetic head involves an electroplating deposition process. Deposition by electroplating, however, limits the choice of materials that can be used for the yoke. For high data rate applications (e.g., operating frequencies greater than 100 MHz), the yoke is preferably a laminated structure having alternating layers of magnetic and non-magnetic materials. This structure helps suppress eddy currents at high operating frequencies which desirably increases the efficiency of the magnetic head. The laminated structure may be deposited using dry process techniques, such as sputter deposition, followed by an ion milling process to pattern the yoke shape.
FIG. 1 is a cross-sectional view of a prior art magnetic head 111 which includes laminated structures to reduce the eddy currents at high operating frequencies. FIG. 2 shows part of the same magnetic head in a top down view. A magnetic portion 150 of the write head includes a first pole piece (P1) 112, a second pole piece (P2) 114, a third pole piece (P3) 126, and a back gap structure 134. First pole piece 112 includes a first pole piece layer 116 and a first pole tip structure 118 formed on top of first pole piece layer 116. First pole piece layer 116 is a horizontally laminated structure having alternating layers of magnetic and non-magnetic materials, as indicated by the horizontal lines within the structure. First pole tip structure 118, which is an electroplated pedestal, is separated from the pole tip of second pole piece 114 by a gap layer 120. Gap layer 120 may be made of alumina (Al2O3) or other suitable non-magnetic material.
Third pole piece 126 is formed partially over second pole piece 114 near the ABS and over back gap structure 134 in the back gap region. Like first pole piece layer 116, third pole piece 126 is a horizontally laminated structure having alternating layers of magnetic and non-magnetic materials, as indicated by the horizontal lines within the structure. Back gap structure 134 is formed between first and third pole pieces 112 and 126 to magnetically couple first, second, and third pole pieces 112, 114, and 126. Back gap structure 134 is an electroplated structure made of a magnetic material.
Conventional write coils 160 are also formed within the magnetic head over an insulator which is on top of first pole piece layer 116. In addition, a read sensor 128 (e.g., a GMR sensor) is sandwiched in between first and second shield layers 124 and 132. A separation layer 122, which is a non-magnetic material, separates second shield layer 124 from first pole piece 112.
As described earlier, the laminated structures having alternating layers of magnetic and non-magnetic materials in first and third pole pieces 116 and 126 help suppress the eddy currents and improve the high frequency performance of the write head. A loss of efficiency is still observed, however, in back gap structure 134 which is not a laminated structure. If back gap structure 134 were a horizontally laminated structure like first and third pole pieces 116 and 126, the eddy currents in the back gap region would still not be reduced significantly. This is because the lamination in first and third pole pieces 116 and 126 is oriented in the same direction as (i.e. parallel with) the magnetic flux, which breaks up the eddy current, whereas the same horizontal lamination in back gap structure 134 would be oriented in a direction perpendicular to the magnetic flux.
Accordingly, there is a resulting need for magnetic heads having back gap structures which suppress eddy currents at high operating frequencies, as well as methods of making the same.